Schottky diode is a metal-semiconductor junction diode with a highly desirable low forward-voltage drop compared to a semiconductor-semiconductor p-n junction diode. Another important advantage of the Schottky Diode is its low reverse recovery time as it is a “majority carrier” semiconductor device. This means that, for example, if the semiconductor body of the Schottky Diode is doped n-type, only the n-type carriers (mobile electrons) play a significant role in normal operation of the device.
FIG. 3 illustrates an example prior art semiconductor junction barrier Schottky (JBS-SKY) diode 10. Referencing an accompanying X-Y-Z Cartesian coordinate system, the prior art JBS-SKY diode 10 has the following major components:                A semiconductor substrate (SCST) 12 with its major plane lying parallel to the X-Y plane. An active device zone (ACDZ) 20 atop the SCST 12. The ACDZ 20 has a built-in junction barrier Schottky (JBS-SKY) diode 24 with its major device current flowing parallel to the Z-axis.        A peripheral guarding zone (PRGZ) 40 atop the SCST 12. While the right hand of the prior art JBS-SKY diode 10 is not shown here to avoid unnecessary obscuring details, for those skilled in the art it should be understood that the PRGZ 40 is located in an adjacent and surrounding relationship to the ACDZ 20 and the PRGZ 40 is structured for the purpose of maintaining a low leakage current and an increased breakdown voltage of the built-in prior art JBS-SKY diode 10.        The active device zone (ACDZ) 20 has an active lower semiconductor structure (ALSS) 22 and an active upper contact structure (UCS) 26 atop the active ALSS 22 with the juncture between active ALSS 22 and UCS 26 forming the aforementioned junction barrier Schottky (JBS-SKY) diode 24.        
As for a more detailed description of these major components, the semiconductor substrate (SCST) 12 is of N++ type conductivity with heavy dopant concentration. The active ALSS 22 has an N-type semiconductor drift layer (SDFL) 22a extended into and through the PRGZ 40 with the top surface portion of ALSS 22 further includes, along an X-Y plane, numerous P+ type surface junction barrier pockets (SJBP) 22b into the SDFL 22a thus forming a junction barrier portion of the JBS-SKY diode 24 with the SDFL 22a. Correspondingly, the PRGZ 40 has numerous peripheral guard rings (PPGR) 22c that, except for being extended into the PRGZ 40 and accordingly patterned, are made of the same material and cross sectioned at the same elevations as the SJBP 22b. The upper part of the PRGZ 40, located just atop the SDFL 22a, has a number of hard mask rings (HMRG) 29a placed in an interdigitated relationship with the PPGR 22c along the X-Y plane. The upper part of the PRGZ 40 also includes a guard ring passivation layer (GRPL) 29b atop and covering the HMRG 29a. In this case, the GRPL 29b is made of low temperature oxide-phosphosilicate (LTO-BPSG) reflow glass.
The prior art UCS 26 has a simple top contact metal (TPCM) 26a. The bottom of UCS 26 includes an intervening barrier metal layer (BRML) 28 between the bottom of TPCM 26a and the top surface of active ALSS 22. The BRML 28 forms, together with a top surface portion of the active ALSS 22, the Schottky diode portion of the built-in JBS-SKY diode 24. Importantly, the BRML 28 also functions as a barrier preventing the TPCM 26a from diffusing into thus poisoning the top surface portion of ALSS 22.
At the top of the prior art JBS-SKY diode 10 is a top device passivation layer (TDPL) 30. The TDPL 30, covering the ACDZ 20 and the PRGZ 40, is patterned with one or more top pad openings (TPO) 30a at pre-determined locations along the X-Y plane, for receiving downward mechanical bonding force 2 during later packaging, for example via wire bonding, of the prior art JBS-SKY diode 10. As a materials example, the TDPL 30 can be made of silicon oxide, silicon nitride or polyimide.
A reliability problem with the prior art JBS-SKY diode 10 is attributable to its post-fabrication packaging. More specifically the bonding force accompanying a wire bonding operation, as illustrated with the downward mechanical bonding force 2, can cause micro cracking of the TPCM 26a at the bottom of the TPO 30a and this in turn allows metal diffusion into thus poisoning the semiconductor material in the top portion of the active ALSS 22, which in turn degrades the original Schottky junction barrier height. The net result is an unacceptably high device leakage current (IDSS) of the packaged prior art JBS-SKY diode 10. In view of this problem, there is a need of improving the prior art JBS-SKY diode 10 for post-packaging reliability.